1. Field of the Invention
The present invention relates generally to an optical disc player which records and reproduces data optically by directing an optical beam onto an optical disc. More particularly, the invention relates to an optical disc player which includes a tracking device for moving the optical beam to a desired point on the optical disc in order to record and reproduce arbitrarily selected data.
2. Description of the Prior Art
As is well known, an optical disc has a plurality of tracks arranged spirally or concentrically. In general, the optical disc is adapted to record information, such as digital video signals, digital audio signals or the like, which data will be referred to hereafter as "information" and data representative of track position on the disc, which data will be referred to hereafter as "address data". The address data specifies the position of a track on which the information is recorded or is to be recorded. The optical disc player directs an optical beam towards the track identified by the address data to record or reproduce the data. In other words, the optical beam is targeted at a point corresponding to the desired track and which is identified by the address data.
In order to radially shift the optical beam toward the desired track identified by the addess data, the conventional technique is to move an optical head block housing an optical transmitter directly to a point near the desired track and thereafter move the optical head block repeatedly track-by-track until it reaches the desired track. In practice, in the initial movement, the optical head block is moved to a position on the disc near the desired track but still about 200 tracks away. After reaching this initial position, the optical head block is repeatedly shifted to the next track in the direction of the desired track in response to track-jump signals which trigger a tracking coil in a tracking device.
This conventional optical head block tracking process has the drawback of taking a rather long time to access the desired track. For instance, it may take approximately 1 msec to shift the optical head block to an adjacent track in response to each track-jump signal. Therefore, shifting the optical head block through 200 tracks may take up to approximately 200 msec.
The present invention is intended to significantly shorten the track-search time for an optical disc.